Cancer, including over 200 diseases, is the second biggest cause of death in the developed countries. Therefore, cancer remains one of the most important unmet medical challenges to mankind. A number of options for treating tumors are available, including surgery, radiation, chemotherapy, or any combination of these approaches. Among these, chemotherapy is widely used for all types of cancers, in particular for those inoperable or with metastatic characteristics. Despite a variety of chemotherapeutic compounds being used in clinics for improvement of survival rates of different human cancers, chemotherapy is generally not curative, but only delays disease progression. Commonly, tumors and their metastasis become refractory to chemotherapy, as the tumor cells develop the ability of multi-drug resistance. In some cases, the tumors are inherently resistant to some classes of chemotherapeutic agents. In other cases, the acquired resistance against chemotherapeutic agents is developed during the chemotherapeutic intervention. Thus, there remain significant limitations to the efficacy of available chemotherapeutic compounds in treating different classes of tumors. Furthermore, many cytotoxic and cytostatic agents used for chemotherapeutic treatment of tumors have severe side effects, resulting in termination of the chemotherapy in some patients. Thus, there remains a need for new chemotherapeutic agents.